*7.3.1 Ash*

Ash is one of the most common product used by smallholder farmers especially in the rural and peri-urban areas. The ash collected from household kitchens or burnt wood [39]. Some use only the dry wood ash while others mix fine dry soil with wood ash. Some others mix their ash with conventional insecticides such as Mocap (ethoprofos or terbufos), cypermethrine or kerosene. Some mix the ash with water or kerosene and used as sprays [39].

Most farmers in Buea Sub-Division, South West Region, Cameroon believe that applying a combination of terbuphos (Counter 10G®) and ash (from rubber plants wood and oil palm bunch residue ash) as seed treatments helps to protect suckers from the banana weevil (*Cosmopolites sordidus*) and stimulate plant growth better than their sole forms [40]. This mixture is mostly applied on soil around the corms or put in the planting holes before planting the plants. Sometimes ash of plant parts are used as insecticide such as the leaves of *Cupressus arizonica*, *Eucalyptus grandis*, *Ocimum gratissimum* and root ash of *Vetiveria zizanioides* against *Sitophilus zeamais* (Coleoptera: Curculionidae) [41]. The ash of *E. grandis* and *O. gratissimum* at the rate of 0.25 g/25 g maize grains significantly reduced the number of emerged weevils but if *E. grandis* ash is increase at 20 g/2 kg grains it significantly reduced grain weight loss and protected grains for 6 months without adversely affecting the germination of the seeds [41].

#### *7.3.2 Essential oils*

Essential oils from so many plant parts have been use as insecticide in Sub Saharan Africa especially in Cameroon. The essential oils are extracted from the seeds, leaves, bark and roots of the plant. Crude essential oils of *Lippia rugosa* and *Hyptis spicigera* are the most promising for *Tribolium castaneum* because of their efficacy on the other life stages. They are more efficient, with 100% mortality, on larvae at early stages and young adults [42]. Oben et al. [39] reported that essential oil from dried seed powder of *Piper guineense* has potentials for development as an organic insecticide against *Sitophilus oryzae* L. and other pests of stored grains. This is because *Piper* carene, copaene, α-caryophyllene or β- caryophyllene with insecticidal propertie [39].

The insecticidal properties of formulations based on *Ocimum gratissimum* essential oil and montmorillonite clay against the maize weevil (*Sitophilus zeamais*). The formulations based on essential oils adsorbed on modified clays is considered as alternatives to synthetic insecticides for use in storage and protection of maize grains from *Sitophilus zeamais* The insecticidal potentials of essential oils of *Chenopodium ambrosioides* and *Cupressus sempervirens* are very effective low persistence against *S. zeamais* on stored maize because persistence of both oils dropped to zero within 2 weeks [43]. In some localities in Cameroon, essential oils of pericarps of ripe fruits from *Citrus aurantifolia, C. limon*, *C. sinensis* and *C. reticulata* are used for the development of natural biocides [44]. *Azadirachta indica* (neem) seeds have been widely used in the northern part of Cameroon as essential oil. *A. indica* seed oils and powders from sun-dried kernels, shade-dried kernels, sun-dried seeds and shade-dried seeds seed oil was more active towards *Callosobruchus maculatus* on cowpea seeds and *Sitophilus zeamais* on maize grains [45].

Essential oils of *Lippia adoensis* leaves have already shown good insecticidal efficacy on *Sitophilus zeamais*. The essential oil of young leaves killed more weevils than that of old leaves, but old leaves were more repellent (II ≤ percent repellency ≤ V) than young leaves (0 ≤ percent repellency ≤ I). With its persistence levels of 98.47% after 96 h, the essential oil of old leaves more persistent than that of young leaves (94.66% after 96 h). The efficacy of essential oil from dry leaves of *Callistemon viminalis* (Myrtaceae) against *Acanthoscelides obtectus* (Say) (Coleoptera; Bruchidae) a major pest of *Phaseolus vulgaris* of stored beans in Cameroon was evaluated and the results revealed that at the end of the first day of exposure, the highest concentrations of essential oil applied to the beans (0.40 μl/g) and to the filter paper discs (0.251 μl/cm<sup>2</sup> ) caused mortality rates of 72.6% and 80%, respectively. These rates increased to 97.5% and 100% respectively after 4 days of exposure.

Essential oils from the leaves of *Ocimum canum* Sims (camphorated basil) and *Ocimum basilicum* L. (sweet basil) caused 100% mortality on *Anopheles funestus* adults at a concentration of 200 ppm for *O. canum* and 250 ppm for *O. basilicum*.

#### *7.3.3 Powder formulation*

In Cameroon some of the method of application is through powder formulation where the plant parts are dried then later grind and may be sieve or not depending on the user. These powders are sometimes mixed with other materials such as wood ash or other plants. The application is done by band placement or broadcasting depending on the farmer. For example in the western highlands of Cameroon plant materials consisting of leaves, seed and/or roots; *Cupressus arizonica*, *Eucalyptus grandis*, *Ocimum gratissimum*, *Vetiveria zizanioides, Balanites aegyptiaca, Lophira lanceolata, Hemizygia welwitschii, Plectranthus glandulosus, Laggera pterodonta* and *Azadirachta in*dica are considered as alternatives to synthetic insecticides for the protection of stored maize grains against *Sitophilus zeamais* [43, 45–47] Dried ground leaves/seed powders of some spices (*Syzygium aromaticum, Piper guineense, Aframomum citratum* and *Ocimum basilicum*), leave/seed powder of *Hemizygia welwitschii* and/or *Plectranthus glandulosus, Azadirachta indica* have an insecticidal potential against the cowpea weevil (*Callosobruchus maculatus*), common bean weevil and maize, thus small-scale farmers have been using them to protect their stored-product [45, 46, 48, 49]. In the Far North region of Cameroon, powders of *Hyptis spicigera* (Lamiaceae), *A. indica* (Meliaceae) and *Vepris heterophylla* (Rutaceae) are mostly used as insecticides single or associated with food during storage in combination with two or three others plants to control the red flour weevil (*Tribolium castaneum*) [50]. The flours from *Phaseolus sativum* and *Phaseolus vulgaris* seeds are also used to protect sorghum grains against the attack of *Sitophilus oryzae* [51].

#### *7.3.4 Aqueous extact*

*Azadirachta indica* (neem) fruit reduces insects' pest in the heading and maturation stages of rice plant [52]. The *aqueous leaves, seeds, roots (aqueous extracts) of Azadirachta indica, Boswellia dalzielii, M. anisopliae, Lippia rugosa, Annona senegalensis and Jatropha curcas* and their combinations are considered as potential natural insecticide in the management of thrips population on *Vigna unguiculata* in the fields. This would increase *Vigna unguiculata* yield and free environmental pollution from synthetic insecticides [53]. Aqueous extracts of *Cannabis sativa, Guibourtia tessannii, Erythrophleum ivorense,Thevetia peruviana, Azadiratchta indica, Ceiba pentandra, Pachyelasma tessmanii, Nicotinia tabacum,* wood ash, *Chnopodium*

*Insecticide Use and Application in Cameroon DOI: http://dx.doi.org/10.5772/intechopen.102634*

*ambrosoides, Lobelia columnaris, Carica papaya, Urtica dioica, Grotolania juncea,* Pepper, as well as smoke from burnt flowers of oil palm and cocoa husks are used in cocoa farms to manage capsids (mirids) and caterpillar infestations. *Cupressus benthanmii, Vetiveria zizaniodes*, *Piper guineense,Tithonia diversifolia, Mucuna cochinchinensis,* garlic, onion, ginger used on tomatoes to reduce population of fruit flies, leaf miners, white flies and caterpillars. *Afromomum melegueta, Piper guineense,* and *A. indica* extracts with greater effectiveness against *C. sordidus*, mealybugs and aphids infesting *Musa* spp. [32]. Extracts of three Cupressus species (*C. macrocarpa, C. sempervirens and C. arizonica*), as well as *Chenopodium ambrosioides* have been shown to have larvicidal and repellent properties against the *Anopheles gambiae* in Cameroon [54, 55].

#### *7.3.5 Plant emulsions*

The insecticidal properties of detergent-oil (mixture of liquid washing detergent and vegetable oil) emulsions of four plants (*Lantana camara, Allium sativum, Coffea arabica,* and *Jatropha curcas*) are used to control mealy bug infestation in banana and plantain field [40].

#### **7.4 Integrated pest management**

Integrated Pest Management (IPM) is a concept that is widely used or documented in diverse literature related to agriculture, environment and pesticides. This concept is becoming more and more popular as people become more and more conscious of the detrimental effects of pesticides and other chemicals used in agriculture, forestry and public health. According to Norris et al. [56], IPM is defined as a decision support system for the selection and use of pest control tactics singly or harmoniously coordinated into a management strategy, based on costbenefit analyses that take into account the interests of and impacts on producers, society, and the environment. Considering this definition IPM can simply be defined as the use of all available pest management techniques or options that are compatible, cost-effective and environment-friendly.

From several discussions (especially with farmers and agriculture officers and researchers), literature and rapid observational assessments, it is clear that on the part of most farmers in the rural areas and a few in urban/peri-urban areas they are applying IPM unknowingly. These farmers have been working for long on the same pieces of land and/or on the same crops. They therefore have some wealth of information about their agro-ecosystems (the behavior of the crops, the different pests and their population dynamics, etc.). With this knowledge, most of these farmers have learnt to apply two or more techniques for managing the pest or pest complexes in their farms. They commonly apply combinations of cultural, physical and chemical options. Those who are flexible have (with the help of agriculture extension workers and researchers) added a genetic component (the use of improved and/or tolerant/resistant varieties) to their management strategy.

In addition, most farmers that are closer to research stations and the large agroindustrial plantations are having extra advantage by considering them as their role models. The farmers cultivate the same crops and put every effort to implement the same IPM strategy that these research stations and the plantations use in their farms. Apart from these hands-on experiences, the farmers (some of which are workers in these research stations and plantations) benefit from the few seminars/ workshops concerning IPM for specific crops and good agricultural practices or best management practices. Such seminars/workshops are very common for crops such

as cocoa, bananas, maize, cotton, and vegetables in peri-urban zones or in areas where pesticide abuse and misuse are common practices.

For the agriculture technicians/extensionists, research technicians, agric/crop protection students, and research assistants/researchers, from time to time they benefit from seminars/workshops/trainings on best management options and good agricultural practices for specific crops or pests. Most of these trainings/workshops are usually organized and sponsored by the Ministries of Agriculture and Health and/or international organizations/research centers such as IITA, CIRAD, IRAD, World Vegetable Centre, FAO, and GIZ. These organizations have played an important role in the implementation of Farmers' Field Schools (FFSs) in some rural areas of the country. For instance, GIZ in collaboration with the Delegations of Agriculture in the South West, Centre, South and Littoral Regions have organized and sponsored FFSs in the major cocoa producing areas. In these FFSs, farmers are taught and followed up in the farms on good agricultural practices and on using of pesticides only when absolutely necessary.

In addition, texts of certain decrees give some information on how biological control and IPM should be carried out. According to these texts, IPM is to be carried out with the following aim in mind; (i) reduce dependency on pesticides, (ii) effective control on the use of pesticides, (iii) reduce the risks resulting from abusive and inappropriate use of pesticides.
